Latest content added for UNT Digital Library Partner: UNT Librarieshttp://digital.library.unt.edu/explore/partners/UNT/browse/?fq=str_degree_discipline:Biology&fq=untl_collection:UNTETD2014-11-08T11:56:31-06:00UNT LibrariesThis is a custom feed for browsing UNT Digital Library Partner: UNT LibrariesImmunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407757/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407757/"><img alt="Immunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes" title="Immunohistochemistry of the Gills of the Channel Catfish Ictalurus Punctatus: Cells and Neurochemicals That May Be Involved in the Control of Cardioventilatory Reflexes" src="http://digital.library.unt.edu/ark:/67531/metadc407757/thumbnail/"/></a></p><p>In teleost fishes the neurochemicals involved in sensing and responding to hypoxia are unresolved. Serotonergic branchial neuroepithelial cells (NECs) are putative O2 chemoreceptors believed to be homologous to the neural crest (NC) derived APUD (amine-precursor uptake and decarboxylation) pulmonary NECs and carotid body type-1 glomus cells. Branchial NECs contain serotonin (5-HT), thought to be central to the induction of the hypoxic cardioventilatory reflexes. However, application of 5-HT in vivo does not elicit cardioventilatory reflexes similar to those elicited by hypoxia. But previous in vitro neural recordings from glossopharyngeal (IX) afferents innervating O2 chemoreceptors in the trout gill show the same discharge response to hypoxic conditions as does that of acetylcholine (ACh) application. This evidence strongly supports the cholinergic hypothesis of chemoreceptor impulse origin rather than a serotonergic-induced impulse origin model. We therefore hypothesized that NECs contain ACh among other neurochemicals in cells belonging to the APUD series. Although serotonergic branchial NECs did not colocalize with ACh using immunohistochemical methods, several populations of ACh and/or tyrosine hydroxylase (TH) (catecholaminergic) positive, dopamine (DA) negative, cells were found throughout the second gill arch of the channel catfish Ictalurus punctatus. In addition, the NC derivation marker zn-12 labelled the HNK-1-like epitope (Human natural killer) expressed by lamellar pillar cells’ collagen column-associated pillar cell adhesion molecules (CC-PCAMs), evidence confirming their hypothesized NC origin.</p>Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407781/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407781/"><img alt="Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio" title="Shortened in Vivo Bioconcentration Factor Testing in Cyprinus Carpio" src="http://digital.library.unt.edu/ark:/67531/metadc407781/thumbnail/"/></a></p><p>Bioconcentration factor testing serves as the most valuable surrogate for the assessment of bioaccumulation. The assessment of potentially harmful chemicals is crucial to not only the health of aquatic environments, but to humans as well. Chemicals that possess the ability to persist in the environment or that have the potential to bioaccumulate, pose a greater risk to organisms that are exposed to these chemicals. The Organization for Economic Cooperation and Development Guideline 305 outlines specific protocols to run an accurate and reliable aquatic flow-through test. However, since its adoption in 1996, very few changes have been made to accommodate the endeavor to lowering the amount of test species to run one of these said tests. Running an aquatic flow-through test, according to 305, takes much time and money as well as numerous amounts of fish. Such burdens can be eliminated through simple modifications to the standard protocols. In this study, we propose an abbreviated study design for aquatic bioconcentration testing which effectively alleviates the burdens of running a flow-through test. Four chemicals were used individually to evaluate the usefulness of the proposed shortened design; 4-Nonyphenol, Chlorpyrifos, Musk Xylene, and DDT. The study consisted of exposing Cyprinus carpio for 7 days followed by 7 days of depuration, for a total of a 14-day study. Our results for each of the four compounds are consistent with literature values, thus, demonstrating that BCFk can be accurately predicted in an abbreviated in vivo test.</p>The Effect of Menthol on Nicotine Metabolism: a Cross Species Evaluation2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407773/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407773/"><img alt="The Effect of Menthol on Nicotine Metabolism: a Cross Species Evaluation" title="The Effect of Menthol on Nicotine Metabolism: a Cross Species Evaluation" src="http://digital.library.unt.edu/ark:/67531/metadc407773/thumbnail/"/></a></p><p>The effect of menthol on nicotine metabolism was examined in liver S9 fractions of four different species and in the in vivo mouse model. The purpose of this study was to investigate three parameters: (1) biotransformation of nicotine to cotinine in various species (human, mouse, rat and trout) using in vitro methods; (2) to determine if the addition of menthol with nicotine altered biotransformation of nicotine to cotinine; (3) and to assess similar parameters in an in vivo mouse model. The major findings of this study include: (1) mice appear to metabolize nicotine, over time, in a manner similar to humans; (2) menthol decreased cotinine production, over time, after a single dose in mice; and (3) menthol increased cotinine production, over time, after repeated doses, in mice.</p>Relationships of Benthic Macroinvertebrate Community Structure with Land-use, Habitat, In-stream Water Chemistry, Depositional Sediment Biofilm Fatty Acids, and Surfactants in the Effluent Dominated Texas Trinity River2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407738/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407738/"><img alt="Relationships of Benthic Macroinvertebrate Community Structure with Land-use, Habitat, In-stream Water Chemistry, Depositional Sediment Biofilm Fatty Acids, and Surfactants in the Effluent Dominated Texas Trinity River" title="Relationships of Benthic Macroinvertebrate Community Structure with Land-use, Habitat, In-stream Water Chemistry, Depositional Sediment Biofilm Fatty Acids, and Surfactants in the Effluent Dominated Texas Trinity River" src="http://digital.library.unt.edu/ark:/67531/metadc407738/thumbnail/"/></a></p><p>The Trinity River is an urbanized, effluent-dominated river, and is heavily relied upon for drinking water. The benthic macroinvertebrate community has been monitored for over 20 years, with the focus of this dissertation on three studies (1987-88, 2005, and 2011). Water quality improvement following dechlorination resulted in increased benthic metrics. Overall habitat quality, in-stream cover, surface water total organic carbon, sediment total organic carbon, near-field urban land-use, near-field forested land-use, surface water surfactant toxic units, and depositional sediment biofilm fatty acids all have statistically significant relationships with benthic macroinvertebrate metrics. These relationships are better defined with increased taxonomic resolution at the genus/species level for all benthic taxa, including Chironomidae and Oligochaeta. It is recommend that benthic identifications for state and city water quality assessments be done at the genus/species level. A novel method for quantifying depositional sediment biofilm fatty acids has been produced and tested in this dissertation. Benthic metrics are directly related to fatty acid profiles, with several essential fatty acids found only at upstream sites.</p>Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis)2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407750/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407750/"><img alt="Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis)" title="Effects of Airway Pressure, Hypercapnia, and Hypoxia on Pulmonary Vagal Afferents in the Alligator (Alligator Misssissippiensis)" src="http://digital.library.unt.edu/ark:/67531/metadc407750/thumbnail/"/></a></p><p>The American alligator (Alligator mississippiensis) is an aquatic diving reptile with a periodic breathing pattern. Previous work has identified pulmonary stretch receptors (PSR), both rapidly- and slowly-adapting, and intrapulmonary chemoreceptors (IPCs) that modulate breathing patterns in alligators. The purpose of the present study was to identify the effects of prolonged lung inflation and deflation (simulated dives) on PSR and/or IPC firing characteristics in the alligator. The effects of airway pressure, hypercapnia, and hypoxia on dynamic and static responses of pulmonary stretch receptors (PSR) were studied in juvenile alligators (mean mass = 246 g) at 24°C. Receptor activity appeared to be a mixture of slowly-adapting PSRs (SARs) and rapidly-adapting PSRs (RARs) with varying thresholds and degrees of adaptation, but no CO2 sensitivity. Dives were simulated in order to character receptor activity before, during, and after prolonged periods of lung inflation and deflation. Some stretch receptors showed a change in dynamic response, exhibiting inhibition for several breaths after 1 min of lung inflation, but were unaffected by prolonged deflation. For SAR, the post-dive inhibition was inhibited by CO2 and hypoxia alone. These airway stretch receptors may be involved in recovery of breathing patterns and lung volume during pre- and post-diving behavior and apneic periods in diving reptiles. These results suggest that inhibition of PSR firing following prolonged inflation may promote post-dive ventilation in alligators.</p>Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407741/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407741/"><img alt="Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna" title="Phototoxic Effects of Titanium Dioxide Nanoparticles on Daphnia Magna" src="http://digital.library.unt.edu/ark:/67531/metadc407741/thumbnail/"/></a></p><p>Titanium dioxide nanoparticles (TiO2-NP) are one of the most abundantly utilized nanomaterials in the world. Studies have demonstrated the mechanism of acute toxicity in TiO2-NP to be the production of reactive oxygen species (ROS) leading to oxidative stress and mortality in exposed organisms. It has also been demonstrated that the anatase crystalline conformation is capable of catalyzing the cleavage of water molecules to further increase the concentration of ROS in the presence of ultraviolet radiation. This photoenhanced toxicity significantly lowers the toxicity threshold of TiO2-NP to environmentally relevant concentrations (ppb). The goal of this study was to determine whether dietary uptake and accumulation of TiO2-NP in the aquatic filter feeder Daphnia magna resulted in photoenhanced toxicity. D. magna and S. caprincornatum were exposed to aqueous solutions of 20ppm and 200ppm TiO2-NP for 24hrs and then transferred to clean moderately hard water. Samples were taken at various time points, dried, and TiO2 quantified using ICP-MS. Toxicity assays were run on D. magna using three TiO2-NP (20ppm, 200ppm) exposure protocols and two ultraviolet radiation treatments. The first exposure group was exposed to aqueous solutions of TiO2-NP for the duration of the test. The second exposure group was exposed to TiO2-NP for an hour and then transferred to clean water. The third exposure group was fed S. capricornatum that had been allowed to adsorb TiO2-NP. All samples were then placed in an outdoor UV exposure system and exposed to either full spectrum sunlight (with UV) or filtered sunlight (no UV). Here we show that TiO2 uptake peaked at one hour of exposure likely due to sedimentation of the particles out of suspension, thus decreasing bioavailability for the duration of the test. Interetsingly, when D. magna were moved to clean water, aqueous concentrations of TiO2 increase as a result of depuration from the gut tract. Data also suggests these excreted particles were bioavailable and re-consumed by D. magna. These data will contribute to the understanding of TiO2-NP environmental fate and toxicity.</p>Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone2014-11-08T11:56:31-06:00http://digital.library.unt.edu/ark:/67531/metadc407838/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc407838/"><img alt="Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone" title="Field and Laboratory Fish Tissue Accumulation of Carbamazepine and Amiodarone" src="http://digital.library.unt.edu/ark:/67531/metadc407838/thumbnail/"/></a></p><p>The goals of this dissertation work were to assess the bioaccumulation potential of carbamazepine and amiodarone, two widely used ionizable pharmaceutical compounds that possess mid-range and high LogD values, respectively, and to evaluate alternative methods to assess chemical accumulation in bluntnose minnows, catfish, and tilapia. Results indicated that carbamazepine does not appreciably bioaccumulate in fish tissue with BCFk and BAF carbamazepine values < 10. Amiodarone, however, with a log D of 5.87 at pH 7.4, accumulated in fish tissues with kinetic BCF values <2,400. Collectively, the data suggest that full and abbreviated laboratory-derived BCFs, BCFMs derived from S9 loss-of-parent assays, as well as field BAF values are similar for each of the two drugs. In summary, the results from this dissertation indicated: 1) The reduced design BCF test is a good estimate for the traditional OECD 305 test. 2) In vitro S9 metabolism assays provide comparable BCF estimates to the OECD 305 test. 3) Metabolism may play a large role in the accumulation of drugs in fish. 4) Reduced BCF tests and in vitro assays are cost effective and can reduce vertebrate testing.</p>Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas2014-04-23T20:20:45-05:00http://digital.library.unt.edu/ark:/67531/metadc283848/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc283848/"><img alt="Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas" title="Endocrine Disruption of Levonorgestrel in Early-life Stages of Fathead Minnows, Pimephales Promelas" src="http://digital.library.unt.edu/ark:/67531/metadc283848/thumbnail/"/></a></p><p>Pharmaceuticals have routinely been detected in the environment resulting in a growing concern about whether these drugs could elicit effects on aquatic organisms. The concerns are centered on the highly conserved nature of mammalian therapeutic targets in fish. These pharmaceuticals are found at very low levels in the environment, which can result in sub-lethal effects in aquatic organisms. Therefore, 28 d early-life stage studies were conducted on six pharmaceuticals to assess their impacts on survival and growth fathead minnow larvae. Two pharmaceuticals tested, carbamazepine and fenofibrate, resulted in no alterations to survival and growth. However, amiodarone, clozapine, dexamethasone, and levonorgestrel (LNG) reduced survival at concentrations tested with LNG being the most potent at 462 ng/L. Survival was increased with amiodarone and clozapine; however LNG significantly decreased growth at 86 ng/L. Therefore, the most potent pharmaceutical tested was the synthetic progestin LNG with survival and growth impacts at concentrations less than 1 μg/L. Further analysis was conducted by measuring specific endocrine related mRNA transcript profiles in FHM larvae following the 28 d ELS exposure to LNG. Transcripts of 3β-HSD, 20β-HSD, and FSH were significantly down-regulated following 28 d exposure to both 16.3 and 86.9 ng/L LNG. Also, CYP19a expression was significantly down-regulated at 86.9 and 2392 ng/L LNG. Subsequently, a second study examined time periods that may be most sensitive (e.g., windows of sensitivity) for FHM larvae exposed to LNG. Larvae were exposed to a single concentration of LNG (i.e. LOECgrowth of 86.2 ng/L as determined in the 28 d ELS study) for different time periods starting with fertilized egg through 28 dph. Growth and mRNA expression of the four differentially expressed transcripts from the first study were measured. Regardless of the duration of exposure, LNG significantly decreased growth in fathead minnow larvae at day 28. For both 20β-HSD and CYP19a, mRNA expression was decreased following exposure to LNG; however, these transcripts returned to baseline levels after removal of LNG. 3β-HSD and FSH showed similar trends after exposure to LNG with 7-14 d and 14-28 d exposures exhibiting a decrease in expression; however, FSH expression returned to baseline once removed for LNG exposure. Based on these data, 3β-HSD was the only transcript to remain down regulated after LNG exposure. Together these data suggest LNG can negatively impact FHM larval survival and growth, with significant alterations in endocrine related responses. However, these changes in endocrine related responses may not directly correlate to the changes in growth demonstrated with LNG exposure to fathead minnows. Therefore, additional research is warranted to ascertain additional mechanisms, either endocrine related or non-endocrine functions, related to changes in growth of larval fathead minnows.</p>Nicotinic Acetylcholine Receptor α3 mRNA in Rat Visual System After Monocular Deprivation2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc278900/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc278900/"><img alt="Nicotinic Acetylcholine Receptor α3 mRNA in Rat Visual System After Monocular Deprivation" title="Nicotinic Acetylcholine Receptor α3 mRNA in Rat Visual System After Monocular Deprivation" src="http://digital.library.unt.edu/ark:/67531/metadc278900/thumbnail/"/></a></p><p>In situ hybridization was used to examine effects of monocular enucleation on
nicotinic acetylcholine receptor subunit cc3 mRNA in the rat dLGNand visual cortex. After 28 days postoperative, there were no significant differences in α3 mRNA density between the contralateral (deprived) and ipsilateral (non-deprived) sides. The lack of obvious effects of visual deprivation on α3 mRNA density suggests that other factors, possibly intrinsic to dLGNand visual cortex, govern the postnatal expression of α3 mRNA.</p>Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela2014-03-26T09:30:20-05:00http://digital.library.unt.edu/ark:/67531/metadc279052/<p><a href="http://digital.library.unt.edu/ark:/67531/metadc279052/"><img alt="Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela" title="Light Spectra Distributions in Temperate Conifer-Forest Canopy Gaps, Oregon and in Tropical Cloud-Forest Canopy, Venezuela" src="http://digital.library.unt.edu/ark:/67531/metadc279052/thumbnail/"/></a></p><p>Light spectra distributions were measured in two different montane forests: temperate and tropical. Spectral light measurements were made in different sized canopy gaps in the conifer forest at H. J. Andrews Experimental Forest in Oregon, USA. Researchers at Oregon State University created these
gaps of 20 m, 30 m, and 50 m in diameter. In the tropical cloud forest, spectral light measurements were made in two plots that were permanently established at La Mucuy Parque Nacional in Venezuela, in collaboration with researchers at Universidad de Los Andes. In both studies, spectra and distributions of physiologically active light were analyzed: red, far-red, R/FR ratio, and blue light.</p>